Wednesday, February 27, 2013

Speer Gold Dot .357 Magnum 158 Grain Stress Test

 
As a follow-up test to a previous test in bare gel, I ran a second test with the 158 grain 357 Magnum load through the leather and denim stress test.  This article recaps that test.  

Test Pistol Specs:
Smith & Wesson 686 +  4" Barrel


Testing Protocol:
My testing process is pretty simple.  I take one shot at the end of a Clear Ballistics Gel block that measures approximately 6" x 6" x 16" and weighs approximately 16 lbs.  I take the test shot from 8 feet away and impact velocity is measured less than 2 inches away from the block.  Clear Ballistics Gel is calibrated to 10% ballistics gel density.  I shoot the block at the range and then bring it home to analyze the block and recover the bullet.  Immediately prior to shooting the block, I take a 5 shot velocity test over a ProChrono Digital chronograph.

Stress tests include an additional barrier of Hermann Oak 5/6 ounce tooling leather and 2 layers of medium weight denim in front of the gel block.


Test Results:
The test results are summarized in the data sheet below along with a close up shot of the recovered bullet.



Video documentation of the entire test from range through bullet recovery is available below.  The high definition video is best viewed on YouTube, but you can also view it here.

My Thoughts on This Load:

In the previous bare gel test, this load did well.  It expanded and penetrated to an amazing 23" in bare gel.  Unfortunately, the results were quite different in the stress test.  If nothing else, it validates that the stress test really does put a considerable amount of stress on the dynamics of bullet expansion.  In the close up picture of the bullet you can see that the petals were trying to expand, but it just didn't happen.  Based on the leather plug recovered from the wound channel, I believe the leather completely plugged the hollow point cavity until the bullet tumbled 180 degrees and the leather plug was dragged out of the bullet nose.  The recovered leather plug actually had a convex shape on one side that exactly matched the concave of the hollow point cavity.

Wrap Up:
While terminal performance was disappointing, there were some new learnings that came out of this test.  The first was that the stress test does indeed live up to the name I gave it.  It is going to be really interesting to see how the future stress tests play out with other loads that performed well in bare gel testing.

The second neat thing was seeing the wound channel left by the tumbling bullet.  Since the bullet tumbled at a high rate of speed, it left a very large permanent wound channel behind it.  I think of it like a log floating down a river and running parallel with the river current.  This log leaves very little disruption in the river when moving along with the current.  Turn that log 90 degrees and put the long side against the current and you've now got a major disruption to the surface of the river. We saw that disruption in the gel block.  

The third, and possibly most interesting, observation from this test was the penetration depth change caused by the bullet tumbling.  In the bare gel test, the expanded bullet traveled 23 inches down the gel block.  In this test, the unexpanded bullet should have penetrated much deeper, but because it tumbled and lost energy it only penetrated to 22.5 inches.
   



Disclaimer....This test should not be considered an endorsement or recommendation for the product(s) tested.  All tests represent actual performance in ballistics testing media.  Terminal performance in all other media will show different results.  It is up to each individual to make their own personal decision on which specific ammunition to use for their needs.  It's also critically important to test any ammo in YOUR SPECIFIC FIREARM before relying on it for any purpose.

Ammunition labeled as +P or +P+ should only be used in firearms that have been certified by the manufacturer as safe for the additional pressures generated by these ammunition types.

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